Process of producing naphthol-sulphonic acids



Patented Apr. 13, 1926,

UNITED STATES PATENT oFF cE,

PAUL H. FALL, 01 CARNEYS POINT, NEW JERSEY, AND IRA E LEE, QF WILMINGTON, I DELAWARE, ASSIGNORS T0 E. I. DU PONT DE NEMOURS & COMPANY, OF WILMING- TON, DELAWARE, A CORPORATION OF DELAWARE.

PROCESS 01E PRODUCING NAPHTI- IOL-SULPHONIC ACIDS.

No Drawing.

To all whom it may concem:

Be it known that we, PAUL H. FALL and IRA E. LEE, citizens of the United States, and residents of Carneys Point, in the countyof Salem and State of New Jersey, and Wilmington, in the county of New Castle and State of Delaware, respectively,

have invented a certain new and useful Process of Producing Naphthol-Sulphonic Acids, of which the following" is a specification.

This invention relates to a process of producing naphthol-sul honic acids from their corresponding sulp lite esters, and consists essentially in heating an aqueous solution of such an ester to hydrolyze the same, and removing from the field of the reaction the acid resulting from the hydrolysis as fast as it is formed. More particularly our invention comprises boiling'an aqeous solution of a sulphite ester of an -alpha-naphthol-monosul honic acid, such as the 1,4- and 1,5- nap tholsulphonic acids, with an alkaline earth metal hydroxide. In the ordinary sulphite process for the preparation of l-naphtholA-sulphonic acid or. l-naphthol-fi-sulphonic acid, both of which may be referred to generically asv a, naphthol-sulphonic acid having the substituents in alpha positions, the sodium salt.

of naphthionic acid (1-naphthylamine-4- sulphonic acid); or of Laurents acid (1- naphthylamine-5-sulphonic acid) is dissolved in warm water, then the resulting solution is treated with a solution of sodium bisulphite by which the sulphite ester of l-naphtholi-sulphonic acid or l-naphtholfi-sulphonic acid is formed, with practically 100% yield. The sulphite ester of l-naphtholi-sulphonic acid or 1-naphthol-5-sulphonic acid is then converted to l-naphtholi-sulphonic acid or I-naphthol-5-sulphonic acid by hydrolysis with caustic soda with a .maximum yield of about 90% of theory,

' provided at least three hydrolyses are carried out. v The steps in the conversion of the aminonaphthalene-sulphonic acid into the corresponding naphtol sulphonic acid, by means Application filed June 30,

of the sulphite process, are made clear by the following equations:

The first of the steps in the process as.

given above, i. e., esterification, goes practically to completion, but the second one, hydrolysis of the sulphite ester to thecorresponding oxy acid with caustic soda, comes to equilibrium long before the reaction is completed (about 65% completed) due to second equilibrium is reached (about 80% of the total ester converted to the oxy body), when the treatment with hydrochloric acid to expel sulphites is again repeated. A third treatment with caustic soda and hydrochloric acid brings the total conversion of the sulphite ester to the cry body to about 90%. During the total hydrolysis there has been formed in solution about one part of salt to one part ofoxy acid, so the reaction is usually stopped at this point. The total time for the above described hydrolysis is from four to five days.

We have now discovered that a remarkable increase in yield of naphthol-sulphonic acid, and decrease in time of hydrolysis, are obtained by carrying out the hydrolysis of ,thesulphite ester in the presence of an hydroxide-such as an alkaline earth metal hydroxide: calcium hydroxide, strontium hydroxide, barium hydroxide, etc.,which is a fairly strong base and yet forms a s'ulhite which is almost insoluble in water.

y the use of the above mentioned bases, we have been able to increase the yield of naphthol-sulphonic acid 'to practically 100% and to decrease the time required for hydrolysis to three hours.

in this case practically 100%,

Our invention may be illustrated in greater detail by the following example:

An aqueous solution of the sulphite ester of l-naphtholl-sulphonic acid, prepared in the well-known manner, above outlined, is brought to a boil and then there is added about one part of dry hydrate of lime for each 4.4? parts of the su'lphite ester (i. e. for each 3.31 parts of sodium naphthionate used at the start). The resulting mixture is boiled for three hours, when the resulting calcium sulphite is filtered oil and washed. The yield of l-napl1thol-4-sulphonic acid is or an increase of about 10% over the maximum obtainable when caustic soda is used for the hydrolysis. Also the time for hydrolysis is 'reduced ,ifrom 4 to 5 days with caustic soda to three hours with lime.

(If barium or strontium hydroxide had been used instead of lime, any excess of base would be precipitated with soda ash and filtered oif at this point; however; the extreme insolubility of lime in hot solution makes such a step unnecessary when it is used The l-naphthol-l-sulphonic acid is then salted out or used directly for the manufacture of azo dyes.

scribed above in considerable detail, it will be understood that conditions of operation may be changed to some extent without departing from our invention. Thus, the hydrolysis may be performed either above or below the normal boiling temperature of the solution; and the hydroxide may be added all at once, or gradually during thecourse of the reaction.

i. A. process of producing a naphthol-sulphonic acid, which comprises hydrolyzing a sulphite ester of said naphthol-sulphonic acid in the presence of a substance capable of reacting with sulphurous acid to form a sulphite relatively insoluble in water.

2. A process of producing an alpha-naphthol-sulphonic acid, which comprises heating a sulphite ester of said acid with a base which forms a sulphite almost insoluble in water. I

3. A process of producing an alpha-naphthol-sulphonic acid, which comprises heat ing a sulphite ester of said acid with the hydroxide of a metal whose sulphite is relatively insoluble in water.

4-. Aprocess of producing an alpha-naphthol-sulphonic acid which comprises heating a sulphite' ester of said acid with suliicient calcium hydroxide to convert all of the sulphite formed by hydrolysis into a sulphite of calcium.

Although the new process has been deassume 5. A process of producing an alpha-naphthol-monosulphonic acid which comprises boiling an aqueous solution of a sulphite ester of said acid in the presence of an bydroxide of a divalent metal whose hydroxide is a fairly strong base.

6. A process ofproducing an alpha-naphthol-sulphonicacid which comprises heating a sulphite ester of said acid with an alkaline earth metal hydroxide.

7. A process of producing a naphthol-sulphonic acid which comprises hydrolyzing, in the presence of the hydroxide of a metal whose sulphite is relatively insoluble in Wa ter, an ester resulting from the combination of an alkali-metal bisulphite with a naphthyl-amine-sulphonate of an alkali-metal.

8. A process of producing a naphthol-sulphonic acid which comprises combining an alkali-metal bisulphite' with a naphthylamine-sulphonate of an alkalimetal, and hydrolyzing the resulting ester by heating an aqueous solution thereof containing a suiiicient amount of an alkaline earth metal hydoxide to react with substantially allot the sulphite formed by hydrolysis.

9. A proc ss of producing lfl-naphtholsulphonic acid which comprises heating the sulphite ester, resulting from the combination of an alkali-metal bisulphite with alpha-naphthyl-amine-4-sulphonic acid, in

the presenceof an alkaline earth metal hydroxide.

10. A process of producing a naphthol sulphonic acid having the substituents in alpha positions which comprises heating the sulphite ester, resulting from the combination of an alkali-metal bisulphite with a' naphthyl-amine-sulphonic acid having the substituents in alpha positions, in the presence of an alkaline earth metal hydroxide.

11. A. process of producing 1,4-naphtholsulphonic acid which comprises heating the sulphite ester of said acid with calcium hydroxide.

7 12. The process which comprises hydrolyzing in the presence of water and an alka line earth metal hydroxide, the compound formed by the combination of sodium bisulphite with sodium alpha-naphthylamine- .sulphonate.

sodium naphthionate.

In testimony whereof we afiix our signatures. 

